Thermoplastic resins represented by polyethylene terephthalate, polytetramethylene terephthalate and the like are used as fibers, films and molded articles hither to, because they have excellent mechanical properties, excellent electrical properties and so on. Further, the mechanical strength and thermal resistance of these thermoplastic polyester resins are highly improved by addition of reinforcing fillers, including glass fibers. Hence the reinforced composition obtained by said method is preferable as a raw material for functional parts.
Recently, a requirement for safety against a fire especially in electrical and electronic fields has been raised. Therefore, an improvement of flame-retardance of resins has been carried out, and resin compositions to which various kinds of flame-retardant are added are commercialized. As flame-retardation methods of polyester-type resin, for example, there are methods disclosed in Japanese Laid-Open Patent Publication No. sho 50-92346 (1975), No. hei4-198357(1992) and No. hei5-140427(1993), in which a method that halogenated polystyrene resin is added to a thermoplastic polyester resin, a method disclosed in Japanese Laid-Open Patent Publication No. sho 50-35257 and No. sho 62-15256 is that a high molecular weight halogenated bisphenol A-type phenoxy resin is added. On the other hand, as a method to add anti-staticity to thermoplastic resin compositions including polyester-type resin, a method of adding conductive carbon black is well known, such method is disclosed, for example, in Japanese Laid-Open Patent Publication No. sho 49-99734.
Generally, in case where a flame-retardant agent and also a flame-retardant aiding agent are added to a thermoplastic resin in order to give the resin with flame-retardant properties, as reported in books (for example, Jin Nishizawa, "Flame-Retardance of Polymer. The Chemistry and The Actual Technology", TAISEISHA), the formulation ratio of Br in a bromine-type compound used as the flame-retardant agent and Sb in an antimony compound used as the flame-retardant aiding agent in the resin, that means, when the weight ratio of Br/Sb is 3/1, the highest flame-retardant effect can be obtained, and if the ratio differs from 3/1, combustion time will prolong extremely and thus becomes difficult to obtain high-retardance.
However, in case when conductive carbon black is added in order to give anti-static properties to the flame-retardant polyester-type composition in which a flame-retardant and a flame-retardant aid have been added as mentioned above, the above-mentioned Br/Sb weight ratio of the flame-retardant and the flame-retardant aid is adjusted to 1/3 to be used as the above-mentioned general ratio, carbonized combustion which is called as glowing may occur in burning. Accordingly it will not meet to the UL94V Standard. To avert it, the amount of the flame-retardant agent and the flame-retardant aiding agent is increased for improving it, the flame-retardant level may be improved a little though, the mechanical strength, thermal resistance and the like of it may be largely lowered.
Under these circumstances, from the above-mentioned viewpoint, the present invention is to provide a polyester-type resin composition which has sufficient anti-static and flame-retardant properties with maintaining the mechanical strength and thermal resistance thereof.